body {
  margin: 0;
  padding: 0;
}

.container {
  margin: 50px 50px;
  overflow: hidden;
}

.item {
  position: relative;
  width: 100%;
  height: 500px;
}

.left {
  width: 100px;
  height: 100%;
  background: skyblue;
}
.right {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: orange;
  margin-left: 100px;
  padding-right: 100px;
  box-sizing: border-box;
}